Field of the Invention
The present invention relates to an electrostatic latent image developing toner and a method of producing the same.
Description of the Related Art
Electrophotographic image forming methods typically use a two-component developer (toner) including colorant-containing toner particles and carrier particles for mixing and carrying the toner particles. Such image forming methods are required to consume less thermal energy during fixation in order to increase the image forming speed and to reduce environmental impact. Therefore, toner particles are required to be fixed at lower temperature. For this purpose, it is generally known to add, to a binder resin, a crystalline resin such as crystalline polyester with high sharp-melting properties.
For example, in a binder resin including a crystalline polyester resin and an amorphous resin, the crystalline part of the crystalline polyester resin melts when the temperature of the binder resin is allowed to exceed the melting point of the crystalline polyester, for example, by heating during fixation. As a result, the crystalline polyester resin and the amorphous resin are compatibilized with each other so that low-temperature fixation of toner particles is achieved. Unfortunately, both resins in such toner particles can be compatibilized at a reaction temperature during the production of the toner particles, which softens the toner particles, so that the resulting toner can have insufficient storage stability.
A known measure to suppress the compatibilization during the production is to add, to a binder resin, a resin containing an introduced nucleating agent having a melting point higher than that of the binder resin. Concerning such a toner, for example, an electrostatic latent image developing toner is known which includes toner base particles including a binder resin, a compound A including a monoester compound, a compound B including at least one selected from a diester compound and a triester compound, and a nucleating agent (see, for example, JP 2013-105128 A).
The introduction of a nucleating agent into toner base particles is effective in facilitating the crystallization of the crystalline resin in the binder resin. On the other hand, however, the nucleating agent is difficult to disperse uniformly in the toner base particles. Therefore, for example, the crystalline resin can crystallize in the vicinity of the surface of the toner base particles, so that the toner particles can have an unsatisfactory level of uniform chargeability.